The invention relates to short messages to be sent in mobile communication systems and particularly to deleting a short message previously sent.
In addition to normal speech and data connections set up on traffic channels in digital mobile communication systems, short digital data messages sent on control and signalling channels of a system, can be transmitted between actual signalling. These messages are generally referred to as short messages. In order to implement short message service mobile communication systems are generally provided with a short message service centre which forwards short messages, and stores and resends short messages that have not been delivered. All short messages pass through a short message service centre. The short message service centre can receive a short message through any network for delivery to a mobile station and a short message formed by means of the keyboard from the mobile station for further delivery to another mobile station or to another destination.
Services offered to subscribers via short messages increase constantly. Several services delivered in text mode may be offered to a subscriber along with short messages. In addition to normal mobile terminating and mobile originating short messages, a subscriber may receive for instance notices, ads and personal reminders.
A short message received at a mobile station is generally stored in the memory of the mobile station, from where a limited number of memory locations is allocated for short messages. A short message remains in the mobile station memory until the subscriber deletes it. A mobile station can receive short messages only when the mobile station is switched on, in the coverage area of the mobile station and when memory allocated for short messages is available.
A problem with the above arrangement is that the sender of the short message cannot herself/himself delete a short message he/she sent from the memory of the receiver. This is particularly annoying both for the sender and the receiver when the short message has become useless for the receiver. An example of such a message is an ad selling coffee at half price during an hour. Another problem is that a useless message unnecessarily allocates memory intended for short messages and eventually prevents the delivery of a more useful short message when the memory becomes full.
One way to prevent the fulfilment of memory locations intended for short messages is to replace the short message sent by the service producer with a new message. A problem with this solution too, is that a useless short message, for example xe2x80x98coffee offer endsxe2x80x99, allocates one memory location if the mobile station subscriber does not delete the message himself/herself. Hence a short message relaying more important information may not be delivered to the receiver, since the memory locations allocated for short messages are filled. A further problem is that the service producer offers poor service by sending useless information that may irritate the receiver.
It is an object of the present invention to provide a solution to the problem mentioned above and to provide a data transmission system where short messages can be deleted remotely controlled. The aim is achieved with a data transmission system, a mobile station, a method and an answering service centre, characterized by what is disclosed in the independent claims.
The term answering service centre refers herein to any speech, fax, data or e-mail box or to another similar mail box receiving messages on behalf of the subscriber and informing the subscriber about a message in the mail box with a short message.
The invention is based on the idea that deletion instructions are sent in a short message, i.e. a deleting short message is sent, which can be a short message deleting a previous one and include a command to delete the previous short message. This allows the sender to remote delete the previously sent short message, which according to the sender has become useless to the receiver. A deleting short message can also be a self-deleting short message including, in addition to a normal text message, an indication of said message being deleted from the memory, for example, in response to reading. A deleting short message provides advantages to the users and producers of answering services in particular. The subscriber no longer needs to remember to delete a short message informing about a message waiting, since the service producer can either after playing the messages send a short message deleting the short message informing about a message waiting from the subscriber memory, or send the short messages informing about the messages waiting as self-deleting short messages. The service producer thus avoids sending useless short messages xe2x80x980 messagesxe2x80x99 and correspondingly the receiver does not need to receive short messages including useless information.
In another preferred embodiment of the invention the deleting short message deletes a previously sent short message in the short message service centre where the previously sent short message waits for delivery. This has the advantage that forwarding a useless message is prevented and signalling can be reduced in the network.
In a further preferred embodiment of the invention the mobile station receives a deleting short message, even if no memory allocated for short messages is available. Then, the message is a short message deleting a previous one. This has the advantage that memory can be released and the message waiting for delivery in the short message service centre can be delivered to the mobile station.
Another advantage of the invention is that the changes needed for implementing the invention can be defined for a distinctly determined area mainly for software controlling the mobile station and the short message service centre. Implementing the invention does not interfere with the operation of such network elements, to which the operation of the invention has not been added.
The preferred embodiments of the data transmission system, the mobile station and the answering service centre of the invention are disclosed in the attached dependent claims.